Arcing grooves in commutator with emery paper

Abstract:

Friction between the copper segments of the commutator and the brushes eventually wears both surfaces. Older copper brushes can cause more wear to the commutator. Copper brushes can cause deep grooves and notches on the surface over time.
The commutator on small motors is not designed to be repaired. On large industrial equipment, the commutator may be re-surfaced with abrasives. Emery paper is like sandpaper. It can be used for sanding down hard and rough surfaces.